Cooling Towers are a symbol of today's modern society. Is there a better alternative?. Industrial Water Cooling
Water is the life blood of all living things on this planet. Just as we use water in our homes for cleaning, drinking, and cooking, industries use water for the same reasons, but on a much larger scale. Industrial water usage in 2005 was an estimated 20 million gallons per day for self-supplied facilities, that’s 151 million half-liter bottles of water every day (1).
Water is used in the industrial processes for the cooling of manufacturing machinery, as well as aiding in the production of metal, wood and paper products, chemicals, and gasoline. The production for many of these industries involves using water for fabrication, washing, diluting, and cooling (2).
Two Methods and There Effects
Industrial plants use water for cooling of equipment. Just like the engine in your car is water jacketed to remove excess heat, power plants and oil refiners, among other industrial applications, also use water in a similar manner. There are two methods used in industrial cooling, the once-through method, and the cooling tower method (3). The once-through cooling method is often used at facilities with access to large bodies of water such as large rivers and oceans. In this method, water in taken from the body of water, run it through a heat exchanger and return the water back to the original body of water. The expelled water is still hot from being used and this can have adverse affects on the local ecology.
Water contains dissolved gasses, such as oxygen and carbon dioxide. Carbon dioxide can be lethal to marine life, concentration of this gas in temperature dependent. At 1°C the lethal carbon dioxide concentration is 120 milligrams per liter of water (mg/L), but when the temperature is at 30°C lethal concentration is decreased by about half, down to about 55mg/L. Fish are also temperature dependent, seasonal water temperature changes direct fish on when to migrate and when to spawn (4).
The second method used for industrial cooling is the use of cooling towers. Cooling towers use large open towers where hot water is pumped into its base, where the hot water is allowed to evaporate into the atmosphere. This system allows for the reuse of water (5), allowing for the use less water for cooling, roughly about a quarter less water than needed for the once-through system.
Even though cooling towers use less water than once through systems, the cooling towers themselves can have harmful effects to the surrounding area. The towers themselves can harbor dangerous bacteria. Due to the warm and humid nature of the towers it makes an ideal habitat for bacteria to grow. The legionella bacterium thrives in such an environment, and can become entrapped in water vapor exiting the tower. When people breathe in this vapor the bacterium resides in the lungs, causing pneumonia. This disease, called Legionnaires' disease (6), affects between 8,000 and 18,000 people in the United States annually.
A resolution
This water is not necessarily polluted, although it can be speculated that the majority of people would not want to source there house hold water from this source. Industrial water use is astounding, using vast amounts fresh water for cooling and other industrial processes that could have been used for domestic use. Using water more efficiently for industrial purposes can make cleaner water that will be less harmful to the environment and people. Ultimately that is the goal to use less water more efficiently to minimize contamination. Although, no permanent solution has been found, using cooling towers is arguably better than the once through method, and as long as proper sanitation requirements are met cooling towers can be environmentally sound solution.
Cooling Towers are a symbol of today's modern society. Is there a better alternative?.
Industrial Water Cooling
Water is the life blood of all living things on this planet. Just as we use water in our homes for cleaning, drinking, and cooking, industries use water for the same reasons, but on a much larger scale. Industrial water usage in 2005 was an estimated 20 million gallons per day for self-supplied facilities, that’s 151 million half-liter bottles of water every day (1).
Water is used in the industrial processes for the cooling of manufacturing machinery, as well as aiding in the production of metal, wood and paper products, chemicals, and gasoline. The production for many of these industries involves using water for fabrication, washing, diluting, and cooling (2).
Two Methods and There Effects
Industrial plants use water for cooling of equipment. Just like the engine in your car is water jacketed to remove excess heat, power plants and oil refiners, among other industrial applications, also use water in a similar manner. There are two methods used in industrial cooling, the once-through method, and the cooling tower method (3). The once-through cooling method is often used at facilities with access to large bodies of water such as large rivers and oceans. In this method, water in taken from the body of water, run it through a heat exchanger and return the water back to the original body of water. The expelled water is still hot from being used and this can have adverse affects on the local ecology.
Water contains dissolved gasses, such as oxygen and carbon dioxide. Carbon dioxide can be lethal to marine life, concentration of this gas in temperature dependent. At 1°C the lethal carbon dioxide concentration is 120 milligrams per liter of water (mg/L), but when the temperature is at 30°C lethal concentration is decreased by about half, down to about 55mg/L. Fish are also temperature dependent, seasonal water temperature changes direct fish on when to migrate and when to spawn (4).
The second method used for industrial cooling is the use of cooling towers. Cooling towers use large open towers where hot water is pumped into its base, where the hot water is allowed to evaporate into the atmosphere. This system allows for the reuse of water (5), allowing for the use less water for cooling, roughly about a quarter less water than needed for the once-through system.
Even though cooling towers use less water than once through systems, the cooling towers themselves can have harmful effects to the surrounding area. The towers themselves can harbor dangerous bacteria. Due to the warm and humid nature of the towers it makes an ideal habitat for bacteria to grow. The legionella bacterium thrives in such an environment, and can become entrapped in water vapor exiting the tower. When people breathe in this vapor the bacterium resides in the lungs, causing pneumonia. This disease, called Legionnaires' disease (6), affects between 8,000 and 18,000 people in the United States annually.
A resolution
This water is not necessarily polluted, although it can be speculated that the majority of people would not want to source there house hold water from this source. Industrial water use is astounding, using vast amounts fresh water for cooling and other industrial processes that could have been used for domestic use. Using water more efficiently for industrial purposes can make cleaner water that will be less harmful to the environment and people. Ultimately that is the goal to use less water more efficiently to minimize contamination. Although, no permanent solution has been found, using cooling towers is arguably better than the once through method, and as long as proper sanitation requirements are met cooling towers can be environmentally sound solution.
For more information on thermal pollution:
Is nuclear power truly "emissions free" and non-polluting? Everything Nuclear Video ; youtube.comInside the cooling tower; youtube.com
Thermal pollution; Wikipedia.org
Thermal pollution; pollutionissues.com
Bibliography
1. Barber, Nancy L. United Geological Survey. [Online] October 2008. [Cited: September 11, 2010.] HYPERLINK "http://pubs.usgs.gov/fs/2009/3098/pdf/2009-3098.pdf" http://pubs.usgs.gov/fs/2009/3098/pdf/2009-3098.pdf .2. Industrial water use. United States Geoloical Survey. [Online] March 30, 2010. [Cited: September 9, 2010.] HYPERLINK "http://ga.water.usgs.gov/edu/wuin.html" http://ga.water.usgs.gov/edu/wuin.html .
3. HighBeam Research, Inc. Reference.com. [Online] 2010. [Cited: September 11, 2010.] HYPERLINK "http://www.reference.com/browse/once+through+cooling?fromAsk=true&o=100074" http://www.reference.com/browse/once+through+cooling?fromAsk=true&o=100074 .
4. Bradshaw, Burton Davidson and Robert W. Thermal Pollution of water systems. American Chemistry Society. [Online] [Cited: September 10, 2010.] HYPERLINK "http://pubs.acs.org/doi/pdf/10.1021/es60008a606" http://pubs.acs.org/doi/pdf/10.1021/es60008a606 .
5. Cooling Towers. Nuclear Tourist. [Online] 20 February, 2006. [Cited: September 9, 2010.] HYPERLINK "%20http:/www.nucleartourist.com/systems/ct.htm" http://www.nucleartourist.com/systems/ct.htm .
6. Legionellosis Resource Site. Center for Disease Control and Prevention. [Online] June 27, 2008. [Cited: September 11, 2010.] HYPERLINK "http://www.cdc.gov/legionella/patient_facts.htm" http://www.cdc.gov/legionella/patient_facts.htm .
Pictorial Credits
Clockwise from top left:1. Britton, Ian. Eggborough coal fired power station in North Yorkshire owned by British Energy. Digital image. Freefoto.com. 21 Mar. 2001. Web. 11 Sept. 2010. < http://www.freefoto.com/preview/13-35-29?ffid=13-35-29&k=Eggborough+coal+fired+power+station >.
2. Britton, Ian. Magnox nuclear power station at Chapelcross. Digital image. Freefoto.com. 12 Sept. 2010 < http://www.freefoto.com/preview/13-16-1?ffid=13-16-1 >.
3. Radius Images. Dead Sockeye Salmon, Adams River, British Columbia, Canada. Digital image. Getty Images. 2010. 12 Sept. 2010 < http://www.gettyimages.com/detail/90140770/Radius-Images >.
4. Pollution Hazard Sign. Digital image. Acobox.com. 2010. 12 Sept. 2010 < http://acobox.com/node/4980?size=_original >.